1. Field of the Invention
The present invention generally relates to a communication receiver, and more particularly to a recoverable Ethernet receiver.
2. Description of Related Art
Ethernets following 10BASE-T, 100 BASE-TX, 1000BASE-T standards, and higher-speed Ethernets, use unshielded twisted pair (UTP) transmission medium. As link speed increases, it becomes more difficult to design the physical layer (PHY), when considering constraints such as multipath fading, pulse/white noise, adjacent/co-channel interferences in wireless channel, or inter-symbol interference (ISI), (near-end or far-end) channel crosstalk, echo or thermal noise in wired channel. In, gigabit Ethernet (1000BASE-T), Trellis-coded modulation (TCM) is used as error control coding (ECC), which may, in theory, achieve a coding gain of 5.6 dB.
Viterbi decoders are commonly used to decode TCM code. However, it is noticed that the target 5.6 dB coding gain cannot be satisfactorily achieved by the conventional transceiver, particularly the transceiver having a separate Viterbi decoder and ISI post-cursor equalizer that may result in error propagation. In order to improve the coding gain, and error propagation, Kamran Azadet discloses a 1-tap lookahead-parallel decision, feedback decoder (LA-PDFD) in “A 1-Gb/s Joint Equalizer and Trellis Decoder for 1000BASE-T Gigabit Ethernet,” IEEE Journal of Solid-State Circuits, Vol. 36, No. 3, March 2001; and U.S. Pat. No. 7,363,576 entitled “Method and Apparatus for Pipelined Joint Equalization and Decoding for Gigabit Communications,” the disclosures of which are hereby incorporated by reference. The scheme disclosed by Azadet, however, cannot effectively improve the coding gain with respect to Ethernet having a link segment length greater than the specified 100 m. In order to resolve this problem, Lin et al. discloses a P-tap parallel decision feedback decoder (PDFD) in U.S. Pat. No. 7,188,302 entitled “Parallel Decision-Feedback Decoder and Method for Joint Equalizing and Decoding of Incoming Data Stream,” the disclosure of which is hereby incorporated by reference.
TCM is a convolutional code, in which relationship highly exists among parts of the codes. Accordingly, error propagation or burst error may occasionally occur at the receiver end, and may even, result in error catastrophe if not detected and recovered in time.
For the foregoing reasons, a need has arisen to propose a novel scheme that can promptly detect and recover from error.